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<h1><a name="ApacheFelixFrameworkLaunchingandEmbedding-ApacheFelixFrameworkLaunchingandEmbedding"></a>Apache Felix
    Framework Launching and Embedding</h1>

<p><em>[This document is based on Felix 1.4.0.]</em></p>

<ul>
    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-introduction"
           title="introduction on Apache Felix Framework Launching and Embedding">Introduction</a></li>
    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-overview"
           title="overview on Apache Felix Framework Launching and Embedding">API Overview</a>
        <ul>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-creatingandconfiguring"
                   title="creating-and-configuring on Apache Felix Framework Launching and Embedding">Creating and
                Configuring the Framework Instance</a></li>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-startinginstance"
                   title="starting-instance on Apache Felix Framework Launching and Embedding">Starting the Framework
                Instance</a></li>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-stoppinginstance"
                   title="stopping-instance on Apache Felix Framework Launching and Embedding">Stopping the Framework
                Instance</a></li>
        </ul>
    </li>
    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-launching"
           title="launching on Apache Felix Framework Launching and Embedding">Launching Felix</a>
        <ul>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-standardlauncher"
                   title="standard-launcher on Apache Felix Framework Launching and Embedding">Standard Felix
                Launcher</a></li>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-customlauncher"
                   title="custom-launcher on Apache Felix Framework Launching and Embedding">Custom Felix Launcher</a>
            </li>
        </ul>
    </li>
    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-embedding"
           title="embedding on Apache Felix Framework Launching and Embedding">Embedding Felix</a>
        <ul>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-hostinteraction"
                   title="host-interaction on Apache Felix Framework Launching and Embedding">Host/Felix Interaction</a>
            </li>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-hostservices"
                   title="host-services on Apache Felix Framework Launching and Embedding">Providing Host Application
                Services</a></li>
            <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-hostserviceusage"
                   title="host-service-usage on Apache Felix Framework Launching and Embedding">Using Services Provided
                by Bundles</a>
                <ul>
                    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-servicereflection"
                           title="service-reflection on Apache Felix Framework Launching and Embedding">Using Bundle
                        Services via Reflection</a></li>
                    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-serviceother"
                           title="service-other on Apache Felix Framework Launching and Embedding">Other Approaches</a>
                    </li>
                </ul>
            </li>
        </ul>
    </li>
    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-caveat"
           title="caveat on Apache Felix Framework Launching and Embedding">Caveat</a></li>
    <li><a href="#ApacheFelixFrameworkLaunchingandEmbedding-feedback"
           title="feedback on Apache Felix Framework Launching and Embedding">Feedback</a></li>
</ul>


<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-introduction"></a></p>

<h1><a name="ApacheFelixFrameworkLaunchingandEmbedding-Introduction"></a>Introduction</h1>

<p>The Apache Felix framework is intended to be easily launchable and
    embeddable. For example, Felix avoids the use of system properties for
    configuration, since these are globals and can cause interference if
    multiple framework instances are created in the same VM. Felix also
    tries to multiplex singleton facilities, like the URL stream handler
    factory. The goal is to make it possible to use Felix in as many
    scenarios as possible; however, this is still just a goal. In other
    words, this is a work in progress and if any issues arise, it would be
    greatly appreciated if they are brought to the attention of the Felix
    community. The next section provides a Felix API overview, while the
    remainder of the document is divided into two sections, one focusing on
    how to launch Felix and one focusing on how to embed Felix into a host
    application.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-overview"></a></p>

<h1><a name="ApacheFelixFrameworkLaunchingandEmbedding-APIOverview"></a>API Overview</h1>

<p>The Felix framework is implemented by the <tt>org.apache.felix.framework.Felix</tt> class or just <tt>Felix</tt>
    for short. As part of the ongoing OSGi specification process, there is
    a movement to standardize the API for launching and embedding OSGi
    framework implementations. The approach is to have the framework
    implement the <tt>org.osgi.framework.launch.Framework</tt> interface, which extends the <tt>org.osgi.framework.Bundle</tt>
    interface. These interfaces provide the necessary means to launch and manage framework instances. The
    <tt>Bundle</tt> interface is defined as:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">public</span> <span class="code-keyword">interface</span> Bundle
{
    BundleContext getBundleContext();
    <span class="code-object">long</span> getBundleId();
    URL getEntry(<span class="code-object">String</span> name);
    Enumeration getEntryPaths(<span class="code-object">String</span> path);
    Enumeration findEntries(<span class="code-object">String</span> path, <span class="code-object">String</span> filePattern, <span
            class="code-object">boolean</span> recurse);
    Dictionary getHeaders();
    Dictionary getHeaders(<span class="code-object">String</span> locale);
    <span class="code-object">long</span> getLastModified();
    <span class="code-object">String</span> getLocation();
    URL getResource(<span class="code-object">String</span> name);
    Enumeration getResources(<span class="code-object">String</span> name) <span class="code-keyword">throws</span> IOException;
    ServiceReference[] getRegisteredServices();
    ServiceReference[] getServicesInUse();
    <span class="code-object">int</span> getState();
    <span class="code-object">String</span> getSymbolicName();
    <span class="code-object">boolean</span> hasPermission(<span class="code-object">Object</span> obj);
    <span class="code-object">Class</span> loadClass(<span class="code-object">String</span> name) <span
            class="code-keyword">throws</span> ClassNotFoundException;
    void start() <span class="code-keyword">throws</span> BundleException;
    void stop() <span class="code-keyword">throws</span> BundleException;
    void uninstall() <span class="code-keyword">throws</span> BundleException;
    void update() <span class="code-keyword">throws</span> BundleException;
    void update(InputStream is) <span class="code-keyword">throws</span> BundleException;
}</pre>
    </div>
</div>

<p>The <tt>Framework</tt> interface is defined as:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">public</span> <span
        class="code-keyword">interface</span> Framework <span class="code-keyword">extends</span> Bundle
{
    void init();
    FrameworkEvent waitForStop();
}</pre>
    </div>
</div>

<p>An additional requirement for framework implementations not captured
    in the interface definitions is that they must implement a public
    constructor that accepts a <tt>Map</tt>, which is used to pass in configuration properties. When you instantiate the
    <tt>Felix</tt>
    class, the resulting object is the actual System Bundle that bundles
    inside the framework will see if they get bundle 0, which is the System
    Bundle as defined by the OSGi specification.</p>

<table class="warningMacro" align="center" border="0" cellpadding="5" cellspacing="8" width="85%">
    <colgroup>
        <col width="24">
        <col>
    </colgroup>
    <tbody>
    <tr>
        <td valign="top"><img src="apache-felix-framework-launching-and-embedding_files/forbidden.gif" alt=""
                              align="absmiddle" border="0" height="16" width="16"></td>
        <td><b class="strong">WARNING</b><br>

            <p>This API is undergoing changes and is not completely finalized, so future changes are possible.</p></td>
    </tr>
    </tbody>
</table>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-creatingandconfiguring"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-CreatingandConfiguringtheFrameworkInstance"></a>Creating and
    Configuring the Framework Instance</h2>

<p>To create a framework instance, simply instantiate the <tt>Felix</tt> class. A newly created framework instance is in
    the <tt>Bundle.INSTALLED</tt> state. You configure the instance by passing the constructor a <tt>Map</tt> containing
    its configurations properties. The configuration map may contain the following OSGi standard properties:</p>

<ul>
    <li><tt>org.osgi.framework.system.packages</tt> - specifies a
        list of packages the system bundle should export from the environment;
        if this is not set, then the framework uses a reasonable default fault.
    </li>
    <li><tt>org.osgi.framework.system.packages.extra</tt>
        - specifies a list of additional packages the system bundle should
        export from the environment that are appended to the packages specified
        in <tt>org.osgi.framework.system.packages</tt>; there is no default value for this property.
    </li>
    <li><tt>org.osgi.framework.bootdelegation</tt>
        - specifies a list of packages that should be made implicitly available
        to all bundles from the environment (i.e., no need to import them);
        there is no default value for this property and its use should be
        avoided.
    </li>
    <li><tt>org.osgi.framework.storage</tt> - specifies the
        path to a directory, which will be created if it does not exist, to use
        for bundle cache storage; the default value for this property is "<tt>felix-cache</tt>" in the current working
        directory.
    </li>
    <li><tt>org.osgi.framework.storage.clean</tt>
        - specifies whether the bundle cache should be flushed; the default
        value for this property is "none", but it can be changed to
        "onFirstInit" to flush the bundle cache when the framework is
        initialized.
    </li>
    <li><tt>org.osgi.framework.startlevel</tt> - specifies the start level the framework enters upon startup; the
        default value for this property is 1.
    </li>
</ul>


<p>Felix also has the following, non-standard configuration properties:</p>

<ul>
    <li><tt>felix.cache.rootdir</tt> - specifies which directory should be used to calculate absolute paths when
        relative paths are used for the <tt>org.osgi.framework.storage</tt> property; the default value for this
        property is the current working directory.
    </li>
    <li><tt>felix.systembundle.activators</tt> - specifies a <tt>List</tt> of <tt>BundleActivator</tt>
        instances that are started/stopped when the System Bundle is
        started/stopped; the specified instances will receive the System
        Bundle's <tt>BundleContext</tt> when invoked.
    </li>
    <li><tt>felix.log.logger</tt> - specifies an instance of <tt>org.apache.felix.framework.util.Logger</tt> that the
        framework uses as its default logger.
    </li>
    <li><tt>felix.log.level</tt> - specifies an integer <tt>String</tt>
        whose value indicates the degree of logging reported by the framework;
        the default value is "1" and "0" turns off logging completely,
        otherwise log levels match those specified in the OSGi Log Service
        (i.e., 1 = error, 2 = warning, 3 = information, and 4 = debug).
    </li>
    <li><tt>felix.startlevel.bundle</tt> - specifies the start level for newly installed bundles; the default value is
        1.
    </li>
    <li><tt>framework.service.urlhandlers</tt>
        - specifies whether or not to activate the URL Handlers service for the
        framework instance; the default value is "&lt;tt&gt;true&lt;/tt&gt;",
        which results in the
        &lt;tt&gt;URL.setURLStreamHandlerFactory()&lt;/tt&gt; and
        &lt;tt&gt;URLConnection.setContentHandlerFactory()&lt;/tt&gt; being
        called.
    </li>
</ul>


<p>The configuration map passed into the constructor is copied and the
    keys are treated as case insensitive. You are not able to change the
    framework's configuration after construction. If you need a different
    configuration, you must create a new framework instance.</p>

<table class="warningMacro" align="center" border="0" cellpadding="5" cellspacing="8" width="85%">
    <colgroup>
        <col width="24">
        <col>
    </colgroup>
    <tbody>
    <tr>
        <td valign="top"><img src="apache-felix-framework-launching-and-embedding_files/forbidden.gif" alt=""
                              align="absmiddle" border="0" height="16" width="16"></td>
        <td><b class="strong">WARNING</b><br>

            <p>Felix <tt>1.4.0</tt> introduced some significant changes to its configuration properties; if you are
                upgrading from a previous version, the <a
                        href="http://felix.apache.org/site/apache-felix-usage-documentation.html#ApacheFelixUsageDocumentation-migrating"
                        title="migrating on Apache Felix Usage Documentation">usage document</a> describes the
                configuration property changes.</p></td>
    </tr>
    </tbody>
</table>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-startinginstance"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-StartingtheFrameworkInstance"></a>Starting the Framework Instance
</h2>

<p>The <tt>start()</tt> method is used to start the framework instance. If the <tt>init()</tt> method was not invoked
    prior to calling <tt>start()</tt>, then it is implicitly invoked from <tt>start()</tt>. The two methods result in
    two different framework state transitions:</p>

<ul>
    <li><tt>init()</tt> results in the framework instance in the <tt>Bundle.STARTING</tt> state.</li>
    <li><tt>start()</tt> results in the framework instance in the <tt>Bundle.ACTIVE</tt> state.</li>
</ul>


<p>The <tt>init()} method is necessary since the framework does not have a {{BundleContext</tt> when it is first
    created, so a transition to the <tt>Bundle.STARTING</tt> state is required to acquire its context (via <tt>Bundle.getBundleContext()</tt>)
    for performing various tasks, such as installing bundles. Note that Felix also provides the <tt>felix.systembundle.activators</tt>
    property that serves a similar purpose. After the <tt>init()</tt> method completes, the follow actions have been
    performed:</p>

<ul>
    <li>Event handling is enabled.</li>
    <li>The security manager is installed if it is enabled.</li>
    <li>The framework is set to start level 0.</li>
    <li>All bundles in the bundle caches are reified and their state is set to <tt>Bundle.INSTALLED</tt>.</li>
    <li>The framework gets a valid <tt>BundleContext</tt>.</li>
    <li>All framework-provided services are made available (e.g., PackageAdmin, StartLevel, etc.).</li>
    <li>The framework enters the <tt>Bundle.STARTING</tt> state.</li>
</ul>


<p>A call to <tt>start()</tt> is necessary to start the framework instance, if the <tt>init()</tt> method is invoked
    manually. Invoking <tt>init()</tt> or <tt>start()</tt> on an already started framework as no effect.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-stoppinginstance"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-StoppingtheFrameworkInstance"></a>Stopping the Framework Instance
</h2>

<p>To stop the framework instance, invoke the <tt>stop()</tt> method, which will asynchronously stop the framework. To
    know when the framework has finished its shutdown sequence, use the <tt>waitForStop()</tt> method to wait until it
    is complete. A stopped framework will be in the <tt>Bundle.RESOLVED</tt> state. It is possible to restart the
    framework, using the normal combination of <tt>init()</tt>/<tt>start()</tt> methods as previously described.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-launching"></a></p>

<h1><a name="ApacheFelixFrameworkLaunchingandEmbedding-LaunchingFelix"></a>Launching Felix</h1>

<p>Launching Felix is fairly simple and involves only three steps:</p>

<ol>
    <li>Define some configuration properties.</li>
    <li>Create an instance of <tt>org.apache.felix.framework.Felix</tt> with the configuration properties.</li>
    <li>Invoke the <tt>org.apache.felix.framework.Felix.start()</tt> method.</li>
</ol>


<p>In reality, the first step is optional, since all properties will
    have reasonable defaults, but if you are creating a launcher you will
    generally want to more than that, such as automatically installing and
    starting bundles when you start the framework instance. The default
    Felix launcher defines reusable functionality to automatically install
    and/or start bundles upon framework startup; see the <a
            href="http://felix.apache.org/site/apache-felix-usage-documentation.html#ApacheFelixUsageDocumentation-configuringfelix"
            title="configuring-felix on Apache Felix Usage Documentation">usage document</a> for more information on
    configuring Felix and on the various configuration properties.</p>

<p>The remainder of this section describes how the standard Felix
    launcher works as well as how to create a custom launcher for Felix.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-standardlauncher"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-StandardFelixLauncher"></a>Standard Felix Launcher</h2>

<p>The standard Felix launcher is very simple and is not intended to
    solve every possible requirement; it is intended to work for most
    standard situations. Most special launching requirements should be
    resolved by creating a custom launcher. This section describes how the
    standard launcher works. The following code represents the complete <tt>main()</tt> method of the standard launcher,
    each numbered comment will be described in more detail below:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">public</span> <span class="code-keyword">static</span> void main(<span
        class="code-object">String</span>[] argv) <span class="code-keyword">throws</span> Exception
{
    <span class="code-comment">// (1) Check <span class="code-keyword">for</span> proper command line usage.
</span>    <span class="code-keyword">if</span> (args.length &gt; 1)
    {
        <span class="code-object">System</span>.out.println(<span
            class="code-quote">"Usage: [&lt;bundle-cache-dir&gt;]"</span>);
        <span class="code-object">System</span>.exit(0);
    }

    <span class="code-comment">// (2) Load system properties.
</span>    Main.loadSystemProperties();

    <span class="code-comment">// (3) Read configuration properties.
</span>    Properties configProps = Main.loadConfigProperties();

    <span class="code-comment">// (4) Copy framework properties from the system properties.
</span>    Main.copySystemProperties(configProps);

    <span class="code-comment">// (5) If specified, use command-line argument as path to bundle cache.
</span>    <span class="code-keyword">if</span> (args.length &gt; 0)
    {
        configProps.setProperty(Constants.FRAMEWORK_STORAGE, args[0]);
    }

    <span class="code-comment">// (6) Create a list <span class="code-keyword">for</span> custom framework activators and
</span>    <span class="code-comment">// add an instance of the auto-activator it <span class="code-keyword">for</span> processing
</span>    <span class="code-comment">// auto-install and auto-start properties. Add <span
            class="code-keyword">this</span> list
</span>    <span class="code-comment">// to the configuration properties.
</span>    List list = <span class="code-keyword">new</span> ArrayList();
    list.add(<span class="code-keyword">new</span> AutoActivator(configProps));
    configProps.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list);

    <span class="code-comment">// Print welcome banner.
</span>    <span class="code-object">System</span>.out.println(<span class="code-quote">"\nWelcome to Felix."</span>);
    <span class="code-object">System</span>.out.println(<span class="code-quote">"=================\n"</span>);

    <span class="code-keyword">try</span>
    {
        <span class="code-comment">// (7) Create an instance and start the framework.
</span>
        m_felix = <span class="code-keyword">new</span> Felix(configProps);
        m_felix.start();
        <span class="code-comment">// (8) Wait <span class="code-keyword">for</span> framework to stop to exit the VM.
</span>        m_felix.waitForStop();
        <span class="code-object">System</span>.exit(0);
    }
    <span class="code-keyword">catch</span> (Exception ex)
    {
        <span class="code-object">System</span>.err.println(<span
            class="code-quote">"Could not create framework: "</span> + ex);
        ex.printStackTrace();
        <span class="code-object">System</span>.exit(-1);
    }
}</pre>
    </div>
</div>

<p>The general steps of the standard launcher are quite straightforward:</p>

<ol>
    <li>The launcher only supports a single, optional command-line
        argument, which is the path to the bundle cache, so check for this and
        issue a usage message it there are more than one arguments.
    </li>
    <li>Load any system properties specified in the <tt>system.properties</tt> file; this file is typically located in
        the <tt>conf/</tt> directory of the Felix installation directory, but it can be specified directly using the
        <tt>felix.system.properties</tt>
        system property. This file is not needed to launch Felix and is
        provided merely for convenience when system properties must be
        specified. The file is a standard Java properties file, but it also
        supports property substitution using <tt>${&lt;property-name</tt>} syntax. Property substitution can be nested;
            only system properties will be used for substitution.</li>
    <li>Load any configuration properties specified in the <tt>config.properties</tt> file; this file is typically
        located in the <tt>conf/</tt> directory of the Felix installation directory, but it can be specified directly
        using the <tt>felix.config.properties</tt>
        system property. This file is used to configure the Felix instance
        created by the launcher. The file is a standard Java properties file,
        but it also supports property substitution using "<tt>${&lt;property-name</tt>}"
            syntax. Property substitution can be nested; configuration and system
            properties will be used for substitution with configuration properties
            having precedence.</li>
    <li>For convenience, any configuration
        properties that are set as system properties will be copied into the
        set of configuration properties to provide an easy way to add to or
        override configuration properties specified in the <tt>config.properties</tt> file.
    </li>
    <li>If there is a single command-line argument, then use that to set the value of
        <tt>org.osgi.framework.storage</tt>; relative paths are relative to the current directory unless the <tt>felix.cache.rootdir</tt>
        property is set.
    </li>
    <li>Create a list to hold custom framework activators and add an instance of
        <tt>org.apache.felix.main.AutoActivator</tt>, which will process <tt>felix.auto.install</tt> and <tt>felix.auto.start</tt>
        configuration properties during framework startup to automatically install and/or start bundles; see the <a
                href="http://felix.apache.org/site/apache-felix-usage-documentation.html#ApacheFelixUsageDocumentation-configuringfelix"
                title="configuring-felix on Apache Felix Usage Documentation">usage document</a> for more information
        configuration properties.
    </li>
    <li>Create the Felix instance passing in the configuration properties, then call <tt>start()</tt>.</li>
    <li>Invoke <tt>waitForStop()</tt> to wait for the framework to stop to force the VM to exit; this is necessary
        because the framework never calls <tt>System.exit()</tt> and some libraries (e.g., Swing) create threads that
        will not allow the VM to exit.
    </li>
</ol>


<p>The framework is not active until the <tt>start()</tt> method is
    called. If no shell bundles are installed and started or if there is
    difficulty locating the shell bundles specified in the auto-start
    property, then it will appear as if the framework is hung, but it is
    actually running without any way to interact with it since the shell
    bundles provide the only means of interaction.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-customlauncher"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-CustomFelixLauncher"></a>Custom Felix Launcher</h2>

<p>This section creates a bare-bones launcher to demonstrate the
    minimum requirements for creating an interactive launcher for the Felix
    framework. This example uses the standard Felix shell bundles for
    interactivity, but any other bundles could be used instead. For
    example, the shell service and telnet bundles could be used to launch
    Felix and make it remotely accessible.</p>

<p>This example launcher project has the following directory structure:</p>

<div class="preformatted">
    <div class="preformattedContent">
<pre>launcher/
   lib/
      org.apache.felix.main-1.4.0.jar
   bundle/
      org.apache.felix.shell-1.0.2.jar
      org.apache.felix.shell.tui-1.0.2.jar
   src/
      example/
         Main.java
</pre>
    </div>
</div>

<p>The <tt>lib/</tt> directory contains Felix' main JAR file, which
    also contains the OSGi core interfaces. The main JAR file is used so
    that we can reuse the default launcher's auto-install/auto-start
    configuration property handling; if these capabilities are not needed,
    then it would be possible to use the framework JAR file instead of the
    main JAR file. The <tt>bundle/</tt> directory contains the shell
    service and textual shell interface bundles that will be used for
    interacting with the framework instance. Note: If you do not launch
    Felix with interactive bundles, it will appear as if the framework
    instance is hung, but it is actually just sitting there waiting for
    someone to tell it to do something. The <tt>src/example/</tt> directory contains the following <tt>Main.java</tt>
    file, which is a very simplistic Felix launcher.</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">package</span> example;

<span class="code-keyword">import</span> java.util.ArrayList;
<span class="code-keyword">import</span> java.util.List;
<span class="code-keyword">import</span> java.util.Map;
<span class="code-keyword">import</span> java.util.HashMap;
<span class="code-keyword">import</span> org.osgi.framework.Constants;
<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
<span class="code-keyword">import</span> org.apache.felix.main.AutoActivator;

<span class="code-keyword">public</span> class Main
{
    <span class="code-keyword">private</span> <span class="code-keyword">static</span> Felix m_felix = <span
            class="code-keyword">null</span>;

    <span class="code-keyword">public</span> <span class="code-keyword">static</span> void main(<span
            class="code-object">String</span>[] argv) <span class="code-keyword">throws</span> Exception
    {
        <span class="code-comment">// Print welcome banner.
</span>        <span class="code-object">System</span>.out.println(<span class="code-quote">"\nWelcome to Felix."</span>);
        <span class="code-object">System</span>.out.println(<span class="code-quote">"=================\n"</span>);

        Map configMap = <span class="code-keyword">new</span> HashMap();
        configMap.put(AutoActivator.AUTO_START_PROP + <span class="code-quote">".1"</span>,
            <span class="code-quote">"file:bundle/org.apache.felix.shell-1.0.2.jar "</span> +
            <span class="code-quote">"file:bundle/org.apache.felix.shell.tui-1.0.2.jar"</span>);
        List list = <span class="code-keyword">new</span> ArrayList();
        list.add(<span class="code-keyword">new</span> AutoActivator(configMap));
        configMap.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list);

        <span class="code-keyword">try</span>
        {
            m_felix = <span class="code-keyword">new</span> Felix(configMap);
            m_felix.start();
            m_felix.waitForStop();
            <span class="code-object">System</span>.exit(0);
        }
        <span class="code-keyword">catch</span> (Exception ex)
        {
            <span class="code-object">System</span>.err.println(<span
            class="code-quote">"Could not create framework: "</span> + ex);
            ex.printStackTrace();
            <span class="code-object">System</span>.exit(-1);
        }
    }
}</pre>
    </div>
</div>

<p>This launcher has all information hard coded in it, unlike the
    default Felix launcher, which loads configuration properties from files
    and performs variable substitution. This simple launcher provides a
    good starting point if the features of the default launcher are not
    necessary. Since very few configuration properties are specified, the
    default values are used. In the case of the framework bundle cache, it
    will use "<tt>felix-cache</tt>" in the current directory.</p>

<p>By breaking down the above source code into small chunks, it is quite easy to see what is going on.</p>

<div class="code">
    <div class="codeContent">
        <pre class="code-java">Map configMap = <span class="code-keyword">new</span> HashMap();</pre>
    </div>
</div>

<p>This simply creates a map to hold configuration properties.</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java">configMap.put(AutoActivator.AUTO_START_PROP + <span class="code-quote">".1"</span>,
            <span class="code-quote">"file:bundle/org.apache.felix.shell-1.0.2.jar "</span> +
            <span class="code-quote">"file:bundle/org.apache.felix.shell.tui-1.0.2.jar"</span>);</pre>
    </div>
</div>

<p>This sets the <tt>AutoActivator.AUTO_START_PROP</tt> configuration property (string value "<tt>felix.auto.start</tt>"),
    which is a space-delimited list of bundle URLs that the framework will
    automatically install and start when the framework starts. However,
    this property key cannot be used as is; it must be appended with a "."
    and then a number, where the number represents the start level for the
    bundle when it is installed. In this particular example, ".1" is
    appended to the property name, thus the two bundles will be installed
    into start level one. This example uses relative <tt>file:</tt> URLs, which will load the bundles from the <tt>bundle/</tt>
    directory assuming that the launcher is started from the root directory
    of the launcher project. It is also possible to specify absolute URLs
    or remote URLs.</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java">List list = <span class="code-keyword">new</span> ArrayList();
        list.add(<span class="code-keyword">new</span> AutoActivator(configMap));
        configMap.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list);</pre>
    </div>
</div>

<p>This above creates a list to hold custom framework activators and adds an instance of <tt>org.apache.felix.main.AutoActivator</tt>
    to it, which will process the auto-install and auto-start configuration
    properties during framework startup. The list of activators is then
    added to the configuration map.</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java">m_felix = <span class="code-keyword">new</span> Felix(configMap);
            m_felix.start();</pre>
    </div>
</div>

<p>These steps create the framework instance and start it. The configuration property map is passed into the
    <tt>Felix</tt> constructor.</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java">m_felix.waitForStop();
            <span class="code-object">System</span>.exit(0);</pre>
    </div>
</div>

<p>These final steps cause the launching application thread to wait for
    the framework to stop and when it does the launching thread calls <tt>System.exit()</tt> to make sure the VM
    actually exits.</p>

<p>The following command compiles the launcher when run from the root directory of the launcher project:</p>

<div class="preformatted">
    <div class="preformattedContent">
<pre>javac -d . -classpath lib/org.apache.felix.main-1.4.0.jar src/example/Main.java
</pre>
    </div>
</div>

<p>After executing this command, an <tt>example/</tt> directory is
    created in the current directory, which contains the generated class
    file. The following command executes the simple launcher when run from
    the root directory of the launcher project:</p>

<div class="preformatted">
    <div class="preformattedContent">
<pre>java -cp .:lib/org.apache.felix.main-1.4.0.jar example.Main
</pre>
    </div>
</div>

<p>After executing this command, a "<tt>felix-cache/</tt>" directory is created that contains the installed bundles,
    which were installed from the <tt>bundle/</tt> directory.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-embedding"></a></p>

<h1><a name="ApacheFelixFrameworkLaunchingandEmbedding-EmbeddingFelix"></a>Embedding Felix</h1>

<p>Embedding Felix into a host application is a simple way to provide a
    sophisticated extensibility mechanism (i.e., a plugin system) to the
    host application. Embedding Felix is very similar to launching Felix as
    described above, the main difference is that the host application
    typically wants to interact with the framework instance and/or
    installed bundles/services from the outside. This is fairly easy to
    achieve with Felix, but there are some subtle issues to understand.
    This section presents the mechanisms for embedding Felix into a host
    application and the issues in doing so.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-hostinteraction"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-Host/FelixInteraction"></a>Host/Felix Interaction</h2>

<p>In the section on <a href="#ApacheFelixFrameworkLaunchingandEmbedding-launching"
                        title="launching on Apache Felix Framework Launching and Embedding">launching</a> Felix above,
    the <tt>Felix</tt> accepts a configuration property called <tt>felix.systembundle.activators</tt>,
    which is a list of bundle activator instances. These bundle activator
    instances provide a convenient way for host applications to interact
    with the Felix framework. The ability offered by these activators can
    also be accomplished by invoking <tt>init()</tt> on the framework instance and the using <tt>getBundleContext()</tt>
    to get the System Bundle's context, but it can be more convenient to use an activator instance.</p>

<p>Each activator instance passed into the constructor effectively becomes part of the System Bundle. This means that
    the <tt>start()</tt>/<tt>stop()</tt> methods of each activator instance in the list gets invoked when the System
    Bundle's activator <tt>start()</tt>/<tt>stop()</tt> methods gets invoked, respectively. Each activator instance will
    be given the System Bundle's <tt>BundleContext</tt> object so that they can interact with the framework. Consider
    following snippet of a bundle activator:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
{
    <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;

    <span class="code-keyword">public</span> void start(BundleContext context)
    {
        m_context = context;
    }

    <span class="code-keyword">public</span> void stop(BundleContext context)
    {
        m_context = <span class="code-keyword">null</span>;
    }

    <span class="code-keyword">public</span> Bundle[] getBundles()
    {
        <span class="code-keyword">if</span> (m_context != <span class="code-keyword">null</span>)
        {
            <span class="code-keyword">return</span> m_context.getBundles();
        }
        <span class="code-keyword">return</span> <span class="code-keyword">null</span>;
    }
}</pre>
    </div>
</div>

<p>Given the above bundle activator, it is now possible to embed Felix
    into a host application and interact with it as the following snippet
    illustrates:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">public</span> class HostApplication
{
    <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
    <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;

    <span class="code-keyword">public</span> HostApplication()
    {
        <span class="code-comment">// Create a configuration property map.
</span>        Map configMap = <span class="code-keyword">new</span> HashMap();
        <span class="code-comment">// Create host activator;
</span>        m_activator = <span class="code-keyword">new</span> HostActivator();
        List list = <span class="code-keyword">new</span> ArrayList();
        list.add(m_activator);
        configMap.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list);

        <span class="code-keyword">try</span>
        {
            <span class="code-comment">// Now create an instance of the framework with
</span>            <span class="code-comment">// our configuration properties.
</span>            m_felix = <span class="code-keyword">new</span> Felix(configMap);
            <span class="code-comment">// Now start Felix instance.
</span>            m_felix.start();
        }
        <span class="code-keyword">catch</span> (Exception ex)
        {
            <span class="code-object">System</span>.err.println(<span
            class="code-quote">"Could not create framework: "</span> + ex);
            ex.printStackTrace();
        }
    }

    <span class="code-keyword">public</span> Bundle[] getInstalledBundles()
    {
        <span class="code-comment">// Use the system bundle activator to gain external
</span>        <span class="code-comment">// access to the set of installed bundles.
</span>        <span class="code-keyword">return</span> m_activator.getBundles();
    }

    <span class="code-keyword">public</span> void shutdownApplication()
    {
        <span class="code-comment">// Shut down the felix framework when stopping the
</span>        <span class="code-comment">// host application.
</span>        m_felix.stop();
        m_felix.waitForStop();
    }
}</pre>
    </div>
</div>

<p>Notice how the <tt>HostApplication.getInstalledBundles()</tt> method
    uses its activator instance to get access to the System Bundle's
    context in order to interact with the embedded Felix framework
    instance. This approach provides the foundation for all interaction
    between the host application and the embedded framework instance.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-hostservices"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-ProvidingHostApplicationServices"></a>Providing Host Application
    Services</h2>

<p>Providing services from the host application to bundles inside the
    embedded Felix framework instance follows the basic approach laid out
    in <a href="#ApacheFelixFrameworkLaunchingandEmbedding-hostinteraction"
          title="host-interaction on Apache Felix Framework Launching and Embedding">above</a>.
    The main complication for providing a host application service to
    bundles is the fact that both the host application and the bundles must
    be using the same class definitions for the service interface classes.
    Since the host application cannot import classes from a bundle, this
    means that the service interface classes <b>must</b> be accessible on
    the class path, typically as part of the host application itself. The
    host application then must export the service interface package via the
    system bundle so that bundles installed into the embedded framework
    instance can import it. This is achieved using the <tt>org.osgi.framework.system.packages.extra</tt> configuration
    property previously presented.</p>

<p>Consider the follow simple property lookup service:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">package</span> host.service.lookup;

<span class="code-keyword">public</span> class Lookup
{
    <span class="code-keyword">public</span> <span class="code-object">Object</span> lookup(<span class="code-object">String</span> name);
}</pre>
    </div>
</div>

<p>This package is simply part of the host application, which is potentially packaged into a JAR file and started with
    the "<tt>java -jar</tt>"
    command. Now consider the following host application bundle activator,
    which will be used to register/unregister the property lookup service
    when the embedded framework instance starts/stops:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">package</span> host.core;

<span class="code-keyword">import</span> java.util.Map;
<span class="code-keyword">import</span> org.osgi.framework.BundleActivator;
<span class="code-keyword">import</span> org.osgi.framework.BundleContext;
<span class="code-keyword">import</span> org.osgi.framework.ServiceRegistration;
<span class="code-keyword">import</span> host.service.lookup;

<span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
{
    <span class="code-keyword">private</span> Map m_lookupMap = <span class="code-keyword">null</span>;
    <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;
    <span class="code-keyword">private</span> ServiceRegistration m_registration = <span
            class="code-keyword">null</span>;

    <span class="code-keyword">public</span> HostActivator(Map lookupMap)
    {
        <span class="code-comment">// Save a reference to the service's backing store.
</span>        m_lookupMap = lookupMap;
    }

    <span class="code-keyword">public</span> void start(BundleContext context)
    {
        <span class="code-comment">// Save a reference to the bundle context.
</span>        m_context = context;
        <span class="code-comment">// Create a property lookup service implementation.
</span>        Lookup lookup = <span class="code-keyword">new</span> Lookup() {
            <span class="code-keyword">public</span> <span class="code-object">Object</span> lookup(<span
            class="code-object">String</span> name)
            {
                <span class="code-keyword">return</span> m_lookupMap.get(name);
            }
        };
        <span class="code-comment">// Register the property lookup service and save
</span>        <span class="code-comment">// the service registration.
</span>        m_registration = m_context.registerService(
            Lookup.class.getName(), lookup, <span class="code-keyword">null</span>);
    }

    <span class="code-keyword">public</span> void stop(BundleContext context)
    {
        <span class="code-comment">// Unregister the property lookup service.
</span>        m_registration.unregister();
        m_context = <span class="code-keyword">null</span>;
    }
}</pre>
    </div>
</div>

<p>Given the above host application bundle activator, the following
    code snippet shows how the host application could create an embedded
    version of the Felix framework and provide the property lookup service
    to installed bundles:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">package</span> host.core;

<span class="code-keyword">import</span> java.util.List;
<span class="code-keyword">import</span> java.util.ArrayList;
<span class="code-keyword">import</span> java.util.Map;
<span class="code-keyword">import</span> java.util.HashMap;
<span class="code-keyword">import</span> host.service.lookup.Lookup;
<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
<span class="code-keyword">import</span> org.osgi.framework.Constants;

<span class="code-keyword">public</span> class HostApplication
{
    <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
    <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
    <span class="code-keyword">private</span> Map m_lookupMap = <span class="code-keyword">new</span> HashMap();

    <span class="code-keyword">public</span> HostApplication()
    {
        <span class="code-comment">// Initialize the map <span class="code-keyword">for</span> the property lookup service.
</span>        m_lookupMap.put(<span class="code-quote">"name1"</span>, <span class="code-quote">"value1"</span>);

        m_lookupMap.put(<span class="code-quote">"name2"</span>, <span class="code-quote">"value2"</span>);
        m_lookupMap.put(<span class="code-quote">"name3"</span>, <span class="code-quote">"value3"</span>);
        m_lookupMap.put(<span class="code-quote">"name4"</span>, <span class="code-quote">"value4"</span>);

        <span class="code-comment">// Create a configuration property map.
</span>        Map configMap = <span class="code-keyword">new</span> HashMap();
        <span class="code-comment">// Export the host provided service <span class="code-keyword">interface</span> <span
                class="code-keyword">package</span>.
</span>        configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES_EXTRA,
            <span class="code-quote">"host.service.lookup; version=1.0.0"</span>);
        <span class="code-comment">// Create host activator;
</span>        m_activator = <span class="code-keyword">new</span> HostActivator(m_lookupMap);
        List list = <span class="code-keyword">new</span> ArrayList();
        list.add(m_activator);
        configMap.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list);

        <span class="code-keyword">try</span>
        {
            <span class="code-comment">// Now create an instance of the framework with
</span>            <span class="code-comment">// our configuration properties.
</span>            m_felix = <span class="code-keyword">new</span> Felix(configMap);
            <span class="code-comment">// Now start Felix instance.
</span>            m_felix.start();
        }
        <span class="code-keyword">catch</span> (Exception ex)
        {
            <span class="code-object">System</span>.err.println(<span
            class="code-quote">"Could not create framework: "</span> + ex);
            ex.printStackTrace();
        }
    }

    <span class="code-keyword">public</span> void shutdownApplication()
    {
        <span class="code-comment">// Shut down the felix framework when stopping the
</span>        <span class="code-comment">// host application.
</span>        m_felix.stop();
        m_felix.waitForStop();
    }
}</pre>
    </div>
</div>

<p>Rather than having the host application bundle activator register
    the service, it is also possible for the the host application to simply
    get the bundle context from the bundle activator and register the
    service directly, but the presented approach is perhaps a little
    cleaner since it allows the host application to register/unregister the
    service when the system bundle starts/stops.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-hostserviceusage"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-UsingServicesProvidedbyBundles"></a>Using Services Provided by
    Bundles</h2>

<p>Using services provided by bundles follows the same general approach
    of using a host application bundle activator. The main complication for
    the host application using a service from a bundle is the fact that
    both the host application and the bundle must be using the same class
    definitions for the service interface classes. Since the host
    application cannot import classes from a bundle, this means that the
    service interface classes <b>must</b> be accessible on the class path,
    typically as part of the host application itself. The host application
    then must export the service interface package via the system bundle so
    that bundles installed into the embedded framework instance can import
    it. This is achieved using the <tt>org.osgi.framework.system.packages.extra</tt> configuration property previously
    presented.</p>

<p>Consider the following simple command service interface for which
    bundles provide implementations, such as might be used to create an
    extensible interactive shell:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">package</span> host.service.command;

<span class="code-keyword">public</span> class Command
{
    <span class="code-keyword">public</span> <span class="code-object">String</span> getName();
    <span class="code-keyword">public</span> <span class="code-object">String</span> getDescription();
    <span class="code-keyword">public</span> <span class="code-object">boolean</span> execute(<span class="code-object">String</span> commandline);
}</pre>
    </div>
</div>

<p>This package is simply part of the host application, which is potentially packaged into a JAR file and started with
    the "<tt>java -jar</tt>"
    command. Now consider the previously introduced host application bundle
    activator below, which simply provides access to the system bundle
    context:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">package</span> host.core;

<span class="code-keyword">import</span> org.osgi.framework.BundleActivator;
<span class="code-keyword">import</span> org.osgi.framework.BundleContext;

<span class="code-keyword">public</span> class HostActivator <span class="code-keyword">implements</span> BundleActivator
{
    <span class="code-keyword">private</span> BundleContext m_context = <span class="code-keyword">null</span>;

    <span class="code-keyword">public</span> void start(BundleContext context)
    {
        m_context = context;
    }

    <span class="code-keyword">public</span> void stop(BundleContext context)
    {
        m_context = <span class="code-keyword">null</span>;
    }

    <span class="code-keyword">public</span> BundleContext getContext()
    {
        <span class="code-keyword">return</span> m_context;
    }
}</pre>
    </div>
</div>

<p>With this bundle activator, the host application can use command
    services provided by bundles installed inside its embedded Felix
    framework instance. The following code snippet illustrates one possible
    approach:</p>

<div class="code">
    <div class="codeContent">
<pre class="code-java"><span class="code-keyword">package</span> host.core;

<span class="code-keyword">import</span> java.util.List;
<span class="code-keyword">import</span> java.util.ArrayList;
<span class="code-keyword">import</span> java.util.Map;
<span class="code-keyword">import</span> host.service.command.Command;
<span class="code-keyword">import</span> org.apache.felix.framework.Felix;
<span class="code-keyword">import</span> org.apache.felix.framework.util.FelixConstants;
<span class="code-keyword">import</span> org.apache.felix.framework.cache.BundleCache;
<span class="code-keyword">import</span> org.osgi.framework.Constants;
<span class="code-keyword">import</span> org.osgi.util.tracker.ServiceTracker;

<span class="code-keyword">public</span> class HostApplication
{
    <span class="code-keyword">private</span> HostActivator m_activator = <span class="code-keyword">null</span>;
    <span class="code-keyword">private</span> Felix m_felix = <span class="code-keyword">null</span>;
    <span class="code-keyword">private</span> ServiceTracker m_tracker = <span class="code-keyword">null</span>;

    <span class="code-keyword">public</span> HostApplication()
    {
        <span class="code-comment">// Create a configuration property map.
</span>        Map configMap = <span class="code-keyword">new</span> HashMap();
        <span class="code-comment">// Export the host provided service <span class="code-keyword">interface</span> <span
                class="code-keyword">package</span>.
</span>        configMap.put(Constants.FRAMEWORK_SYSTEMPACKAGES_EXTRA,
            <span class="code-quote">"host.service.command; version=1.0.0"</span>);
        <span class="code-comment">// Create host activator;
</span>        m_activator = <span class="code-keyword">new</span> HostActivator();
        List list = <span class="code-keyword">new</span> ArrayList();
        list.add(m_activator);
        configMap.put(FelixConstants.SYSTEMBUNDLE_ACTIVATORS_PROP, list);

        <span class="code-keyword">try</span>
        {
            <span class="code-comment">// Now create an instance of the framework with
</span>            <span class="code-comment">// our configuration properties.
</span>            m_felix = <span class="code-keyword">new</span> Felix(configMap);
            <span class="code-comment">// Now start Felix instance.
</span>            m_felix.start();
        }
        <span class="code-keyword">catch</span> (Exception ex)
        {
            <span class="code-object">System</span>.err.println(<span
            class="code-quote">"Could not create framework: "</span> + ex);
            ex.printStackTrace();
        }

        m_tracker = <span class="code-keyword">new</span> ServiceTracker(
            m_activator.getContext(), Command.class.getName(), <span class="code-keyword">null</span>);
        m_tracker.open();
    }

    <span class="code-keyword">public</span> <span class="code-object">boolean</span> execute(<span class="code-object">String</span> name, <span
            class="code-object">String</span> commandline)
    {
        <span class="code-comment">// See <span class="code-keyword">if</span> any of the currently tracked command services
</span>        <span class="code-comment">// match the specified command name, <span class="code-keyword">if</span> so then execute it.
</span>        <span class="code-object">Object</span>[] services = m_tracker.getServices();
        <span class="code-keyword">for</span> (<span class="code-object">int</span> i = 0; (services != <span
            class="code-keyword">null</span>) &amp;&amp; (i &lt; services.length); i++)
        {
            <span class="code-keyword">try</span>
            {
                <span class="code-keyword">if</span> (((Command) services[i]).getName().equals(name))
                {
                    <span class="code-keyword">return</span> ((Command) services[i]).execute(commandline);
                }
            }
            <span class="code-keyword">catch</span> (Exception ex)
            {
                <span class="code-comment">// Since the services returned by the tracker could become
</span>                <span class="code-comment">// invalid at any moment, we will <span
            class="code-keyword">catch</span> all exceptions, log
</span>                <span class="code-comment">// a message, and then ignore faulty services.
</span>                <span class="code-object">System</span>.err.println(ex);
            }
        }
        <span class="code-keyword">return</span> <span class="code-keyword">false</span>;
    }

    <span class="code-keyword">public</span> void shutdownApplication()
    {
    {
        <span class="code-comment">// Shut down the felix framework when stopping the
</span>        <span class="code-comment">// host application.
</span>        m_felix.stop();
        m_felix.waitForStop();
    }
}</pre>
    </div>
</div>

<p>The above example is overly simplistic with respect to concurrency
    issues and error conditions, but it demonstrates the overall approach
    for using bundle-provided services from the host application.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-servicereflection"></a></p>

<h3><a name="ApacheFelixFrameworkLaunchingandEmbedding-UsingBundleServicesviaReflection"></a>Using Bundle Services via
    Reflection</h3>

<p>It possible for the host application to use services provided by
    bundles without having access to the service interface classes and thus
    not needing to put the service interface classes on the class path. To
    do this, the host application uses the same general approach to acquire
    the system bundle context object, which it can use to look up service
    objects. Using either an LDAP filter or the service interface class
    name, the host application can retrieve the service object and then use
    standard Java reflection to invoke methods on the service object.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-serviceother"></a></p>

<h3><a name="ApacheFelixFrameworkLaunchingandEmbedding-OtherApproaches"></a>Other Approaches</h3>

<p>The <span class="nobr"><a href="http://code.google.com/p/transloader/" title="Visit page outside Confluence"
                             rel="nofollow">Transloader<sup><img class="rendericon"
                                                                 src="apache-felix-framework-launching-and-embedding_files/linkext7.gif"
                                                                 alt="" align="absmiddle" border="0" height="7"
                                                                 width="7"></sup></a></span> project is another attempt
    at dealing with issues of classes loaded from different class loaders and may be of interest.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-caveat"></a></p>

<h1><a name="ApacheFelixFrameworkLaunchingandEmbedding-Caveat"></a>Caveat</h1>

<p>The code in this document has not been thoroughly tested nor even
    compiled and may be out of date with respect to the current Felix
    source code. If you find errors please report them so the that they can
    be corrected.</p>

<p><a name="ApacheFelixFrameworkLaunchingandEmbedding-feedback"></a></p>

<h2><a name="ApacheFelixFrameworkLaunchingandEmbedding-Feedback"></a>Feedback</h2>

<p>Subscribe to the Felix users mailing list by sending a message to <span class="nobr"><a
        href="mailto:users-subscribe@felix.apache.org" title="Send mail to users-subscribe@felix.apache.org"
        rel="nofollow">users-subscribe@felix.apache.org<sup><img class="rendericon"
                                                                 src="apache-felix-framework-launching-and-embedding_files/mail_small.gif"
                                                                 alt="" align="absmiddle" border="0" height="12"
                                                                 width="13"></sup></a></span>; after subscribing, email
    questions or feedback to <span class="nobr"><a href="mailto:users@felix.apache.org"
                                                   title="Send mail to users@felix.apache.org" rel="nofollow">users@felix.apache.org<sup><img
            class="rendericon" src="apache-felix-framework-launching-and-embedding_files/mail_small.gif" alt=""
            align="absmiddle" border="0" height="12" width="13"></sup></a></span>.</p>
</div>
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